1. Field of the Invention
The present invention relates to a semiconductor device, in particular, to a semiconductor device of which a semiconductor package is flexibly mounted and electrically connected to a wiring substrate.
2. Description of the Related Art
To mount a semiconductor package on a wiring substrate as a motherboard, a solder layer composed of for example Sn--Pb should be formed on at least one of the semiconductor package side and the wiring substrate side by a plating method, a printing method, or the like. Thereafter, the solder layer should be heated and melted (re-flowed). With the melted solder as an adhesive agent, the semiconductor package and the wiring substrate are mechanically and electrically connected.
However, such a mounting method for a semiconductor package has the following problems. To heat and melt the solder layer, since an expensive unit referred to as re-flow furnace is used, the cost of the fabrication facility is high. In addition, when solder is re-flowed, since the semiconductor package is exposed to a high temperature environment, the quality of the resultant semiconductor device against high temperature should be assured. Thus, a heat resisting material that is expensive should be used. Moreover, since the solder contains lead that is harmful to human bodies, it should be used and discharged with special attention against protection of environmental contamination.